ssh: handshake failed: knownhosts: key mismatch

After upgrading Flux to 2.6.x, bootstrapping with SSH auth can fail with 'ssh: handshake failed: knownhosts: key mismatch'. Fix: get the ECDSA host key with ssh-keyscan -t ecdsa and update the known-hosts secret, the maintainer confirmed this resolves it. The underlying fix also shipped in source-controller (PR #1828), so updating Flux past that release is the durable fix. Rolling back to 2.5.1 is only a stopgap.

Source: gh:fluxcd/flux2#5385 (Flux CD)

In gh:fluxcd/flux2#5385, the issue was: ### Describe the bug After upgrading from 2.5.1 to 2.6.x, we are no longer able to bootstrap a new cluster when using ssh auth. The source controller is erroring out with the following message: `` failed to checkout and determine revision: unable to list remote for 'ssh://git@REPOSITORY_URL': ssh: handshake failed: knownhosts: key mismatch Rolling back to 2.5.1 solves the issue. ### Steps to reproduce We are using terraform, helm and flux-operator to bootstrap the cluster. Terraform code is below: ``hcl # operator deployment # # Create the flux-system namespace.. The verified answer: After upgrading Flux to 2.6.x, bootstrapping with SSH auth can fail with 'ssh: handshake failed: knownhosts: key mismatch'. Fix: get the ECDSA host key with ssh-keyscan -t ecdsa and update the known-hosts secret, the maintainer confirmed this resolves it. The underlying fix also shipped in source-controller (PR #1828), so updating Flux past that release is the durable fix.. Issue URL: https://github.com/fluxcd/flux2/issues/5385